Sadly, I wouldn't have a clue.
I would like to think that in 6 months, the DDi will be functioning well. The Character Builder is getting there, if far slower than it should have. Surely 6 months is enough to restore (and expand) the Monster Builder to where it should be?
A possible underlying motivation is when a 5E comes along, they can remove the web only 4E DDI character builder immediately and replace it with a new web only 5E version. Anybody who still wants to play 4E, will have to resort to using either the unsupported "ancient" offline 4E DDI character builder or go back to doing character creation by "hand" from the 4E rulebooks.
They could do this, or they could keep updating DDI for 5E simultaneously keeping the 4E data online so that whether you stick with 4E or move on to 5E, you're still handing them $$$ every month.
Imagine if 3.5 had a DDI program? WotC could have their $$$ every month even if they didn't convert to 4E.
In fact, if WotC were smart, they'd add 1E, 2E and 3E to their online tools (sort of like how the VT allows you to choose which edition you play - although functionally it's irrelevant).
Imagine if you could pay a monthly fee to play any edition of D&D released, ever.
I'd do that in heartbeat.
I would want new adventures, new rules supplements, etc. But I would buy in, for sure.
Yeah, to clarify, I didn't mean new content (outside of the current edition). Just coding the old content into a digital reservoir with monthly pay access.
Oh, I see. Well, that's useless to me. I already have all the first edition releases. Why would I wanna pay for something I already have.