Without warning, FTDNA dropped all BigY matches and the availability of BAM files in October, 2017. Then in November, they offered a new BigY-500 test that includes a free upgrade to y111 (from y37 or higher). Now the long rumored product BigY-500 is here. Here is a list of the changes from the standard BigY of before:
(1) Double the SNPs extracted
(2) Now includes the y111 STR panels (new orders)
(3) 389 to 450+ additional STRs extracted
(4) Using HG38 model (was HG19)
The original BigY is no longer available.

UPDATE: In similar fashion, with a transition period, a new BigY-700 test has been introduced a year later to replace the BigY-500. Unlike with BigY-500 introduction though, older kits are not being post-processed for some of the new features. In fact, this is really a completely new test with new equipment and chemistry. As the new name implies, the STR values extracted are upped to over 700 now. But key also is there is a more complete coverage of SNPs across the stable, testable areas of the Y chromosome. Because this is really a new test, they cannot really post-process and upgrade older kit results. They are offering a deeply discounted, "upgrade" price to encourage BigY/BigY-500 testers to additionally test with this refined, deeper test. Once ordered and completed, the old BigY results are removed and replaced with the new results.

Old tests have been upgraded except any of the y111 STRs not separately ordered and paid are not included. You still have to order those panels to get those results. STRs above y111 are all included for anyone who previously ordered the BigY test. (note: new BigY-500 and BigY-700 orders include all the old STR panels. Just upgrades do not include the lower y111 panels. But that can be ordered for $29 via a request to customer service.)

We are still awaiting the BAM file release. Even VCF files have been pulled from availability and are not yet available (again). (UPDATE: BAM and VCF files made available again. VCF are all in HG38. But BAM is HG38 only for new tests ordered as BigY-500; those from before October 2017 are still only HG19. Not clear if HG38 will ever be released for the older tests.)

y500+ STRs are not available in a project chart view as of yet. They can only be viewed in individual kit home pages. And that in the fancy web chart format; not a CSV downloadable file or cut-and-paste table. yFull offers a summary comparison of the expanded STRs that they have been providing. A similar summary is now only available from FTDNA in the match list chart for STR matches. A column has been added to give the number matching across the number compared.

Not all 389+ STRs can be reliably extracted and the set available differs with each tester. Not clear if any base set of STRs will consistently be there. (The problem of extracting STRs from Sequencing testing is that the test process only reads short strands of 100 base-pairs or less. Often, the STR can exceed that read length and so an accurate read / mapping of result strands read cannot be mapped to the model. Many of the STRs in the y111 panels are not reliably read by Sequencing short segment testing. Hence why FTDNA has decided to only test their core, base y111 STRs using their traditional panels.)

As a result of the greater increase in SNPs extracted, the BigY match lists have dramatically shrunk. Wait, what? Many BigY result files are now at well over 300,000 SNPs; a doubling of previous results. Match lists have shrunk because, for many, the novel variants count has risen above the mis-match limit of 30 that FTDNA set. So you can only see much closer matches and not others; even others placed near you on the tree. Often only those very close and in your terminal on the tree are available to you as matches. (Depends on how well the tree is developed in your branching area. If the tree is not well developed, then those near you on the phylogenetic tree will actually be more ancient relatives and thus not match as closely as their new algorithm limit requires.)

Likely much tree restructuring will result. They have automated their tree build, like yFull and yTree has in the past, it appears. Not many new terminals have been introduced for most (yet). But many branches have expanded to match or exceed these found in the other trees like yFull. [UPDATE: Most areas of the tree are now much more detailed than the other sites as they have more test kits to compare against. Not enough have tested with other companies and not FTDNA that then uploaded to the other sites. FTDNA does not accept uploads of Sequencing yDNA tests from other test companies. An exception constantly happening is the inclusion of ancient tests done in studies where the results are available in the public domain. yFull has been added many of these samples to the tree which has led to a lot of restructuring and new knowledge of ancient human movement.])

Still no definitions of SNPs although they can be individually extracted, with effort, from the results page of a user with that allele. [UPDATE: FTDNA has released their SNP list by periodically posting to the ISOGG website. See FTDNA BY SNP Naming Spreadsheet and now the BigY-700 FTDNA FT SNP Naming Spreadsheet).

Resources for Additional Reading (UPDATED)