Lukas is making another attempt at jumpstarting PDO development. I welcome this effort, and will do what I can to help fill in details and make suggestions. Unfortunately, I'm just way too busy with work to be able to commit to more than that.
I also wanted to share some of my thoughts on why PDO has been in a holding pattern for a while, so that more people are aware of it and can work to avoid repeating the same mistakes.
The first thing to note is that the guts of PDO were hard to develop. The PHP script facing API sounds simple enough, but the underlying libraries for each different databases work in different ways, and it was and is a challenge to build PDO in such a way that it can work in the most efficient way.
The second thing, which is really a follow-on from the first, is that the database libraries are complex and nuanced. Some are relatively simple (especially SQLite and MySQL) and others are complex in divergent ways (ODBC and Oracle). Making a great PDO necessitates having experts in each of those APIs and databases around as contributors, both for the core implementation and for unit tests.
Thirdly, there are a lot of databases out there. That requires a lot of resources for the PDO developers to do a good job; not just different database products, but also different versions of those products, need to be tested against. This is also very time consuming.