'As my friends say, be careful what you ask him [me].'

I think the answer to your question is in the tea leaves.

The SS team may have improved ado (and therefore adp) in sql08 but perhaps only as a side effect of attempting to fix issues for non-Access users of ADO. (I don't know anything about this.)

At the time, ADO was introduced to MSACCESS, JET (both Jet 'BLUE' - the Office/VB version and JET 'RED' - the engine used for Exchange) were both 'owned' by the same part of MS that owns SS (if I correctly understood something I read elsewhere). That group wanted to replace Jet RED with SQL (remember the unmet promises for Exchange 2003 and 2007?) and wanted to replace Jet BLUE with things like MSDE. They even went so far in Office2000 as making ADO the default protocol. However, by Office2003, this was no longer 'preferred' and in 2006, one of the top product managers on the MSACCESS team told me that they weren't 'recommending' ADO and ADP anymore (but not discouraging it, either). Another top hand in testing explained publicly in 2006 that his 'favorite' flavor was DAO due to the greater flexibility. They seemed to be nudging folks toward that old-style religion while trying not to offend the other sect. The MSACCESS team seemed to be hinting that DAO and MDB (pre-Office2007) was an advisable strategic move, at least for the middle future (i.e, into Office2007).

You might Google or Live to find a lengthy and hot thread between Michael Kaufman (formerly on the Access Dev Team) and Jamie Collins (I think) (also currently an MS employee), on Michael's blog (also check the still 'up' but mostly dormant site of his former firm -Trigeminal Software) about the religious controversy of ado vs. dao (maybe a year ago). You will learn that MS introduced ADO to MSACCESS to replace DAO [on the way to replacing ADO (and MDBs?)]. But, it didn't and therefore won't.

I spoke with Michael about this just two days ago. Here is his reading of the tea leaves: The Office (MSACCESS) team now 'owns' DAO and JET 'blue'. They wouldn't have acquired it if they didn't have plans. And, we see they did. ACCDB is a superset of MDB. Thus, the announced cessation of enhancement that accompanied the introduction of JET 4.0 is no longer operative. His take seems (to me) to be that since that is what they own and where they invested (creating ACCDB), this is an important part of their future. In addition, he thinks the future of ADO may be moving away from MSACCESS as he feels that ADO 'plus' as he put it, is not so compatible as the older architecture of ADO.

However, DAO may not be their entire future since, clearly, OFFICE generally is working hard to utilize WSS (and thereby SQLServer) as a backend. The fact that Gate's sole remaining functional role in s/w dev at MS is with the Office line implies to me that we should expect to see much more innovation (including in the backend) from them in OFFICE14 and beyond.

I rub elbows (actually their elbows almost reach the top of my head) with several VERY accomplished and successful commercial ACCESS developers who seem to be betting their business on DAO/MDB and using SQL (Express or higher) as a back-end where needed. They don't GENERALLY (not to say EVER) see ADO/ADP as the better path. These folks are also 'inside' MSACCESS, being used by the team to vet new features, strategies, etc. years ahead of product release. My surmise from observing the behaviour of these expert, experienced and best informed practioners is to go with MDB/DAO model. BTW, they don't like the multi-valued fields of ACCDB but will use it over MDB where other 'extended' features are useful.