Problem is that the D&D business unit is currently bringing in negligible sales to Hasbro, and is investing very heavily in R&D.
I don't think you can say that with certainty. As others have said, there's a lot more to the D&D brand than game rulebooks, and DDI is the holy grail: a stable income stream.
Also, with Monte gone, I don't see them investing heavily in R&D. I see them redirecting their existing R&D to D&D.next, but if DDI is the income stream I think it is, it's not a cash investment. I suspect the real investment will come when they start buying art and marketing.
Still, I think Gencon 2013 is a reasonable bet. Mearls said 6-8 months for the playtest, which gives them 7-9 months for finalizing design & development, writing, art, layout, copyediting, indexing, printing, and shipping. Tight, but doable. And the 40th anniversary is a marketing opportunity not to be missed.
One thing we won't see when D&D.next is released? Competent digital offerings. 7-9 months is not enough time for WotC to produce software, unless they've magically gotten a lot more savvy than they used to be. I think we'll see a Compendium alternative at best, but nothing like 4e's character builder.