The decision to put out new, erratta'd printings of the 3.5 Core, including asking what other books folks want, seems like a very strange choice for WotC.
From a purely commercial standpoint, it makes more sense than the 1E reprints.
Look at the used market: 1E core rulebooks can be had very, very cheaply. 3E core rulebooks, OTOH, are much more expensive. And, in the case of the 3.5 PHB, the price for even the lowest quality used copies have been higher than the original MSRP for years now. That tells you that the demand for 3.5 books is outstripping the current supply.
The 1E reprints will only sell to people interested in them as collector's items. A lot of people buying the 3.5 reprints, however, will be buying them because they want to play with them.
(Of course, copies of the 1E reprints will also be used in play. But that won't be the primary reason for purchase: If it were, those people would have already been buying the cheap copies of the originals that are available.)
This, BTW, is why the news that PF was outselling 4E (and doing so consistently) was so devastating for WotC. Although the market numbers are scant and poor, the indications are
very clear that there's still a substantial number of 3.5 players who never migrated to PF. It's hard to say how large that market is, exactly, but if PF is larger than 4E all by itself, the fact that there's another substantial body of non-PF players who didn't migrate to 4E means that 4E only succeeded at converting a significant minority of existing D&D players.
I bring this up because it also suggests the other reason WotC is reprinting 3.5: They're going to have a very tough time converting PF players back to the D&D fold. (For reasons discussed at length
here. Converting 3.5 players will also be tough at this point, but will probably be considerably easier than PF players.
By reprinting the 3.5 core rulebooks now, WotC is actively re-engaging those lost customers. In combination with other olive branches reversing the massively unpopular decisions that surrounded the release of 4E (like bringing back the sales of PDFs), it becomes part of an over-arching strategy to mend bridges.
It's also possible that WotC is hoping that D&D Next will be compatible enough with previous editions that the supplement line can be sold to everybody. I'm highly skeptical of that, but making those core rulebooks available would also make sense under this strategy.