Possibly twice that if 4E had been OGL and Paizo was backing it too. Half the D&D market WotC hoped to have for 4E (maybe more) doesn't play 4E and WotC seems to want to correct that. Could they hit those numbers you claim or even more if they made 5E OGL and coax Paizo back on board? We will see. As to the claim that a 5E OGL and 5E DDI don't play nice together, that's obviously only if they make the DDI something that won't play nice. If they make 5E OGL, I'm sure they'll find a way to make the DDI accomodating to the OGL. It only needs to be worked from that side, since the OGL would work fine with a DDI and online tools that allowed some individual customization and sharing of OGC between DDI users. The only reason the online tools didn't work with OGC in the past is because the online tools were made to not work with OGC.
How?
This is the question I keep asking and no one seems to be able to answer it.
How can you have a d20 OGL, and a DDI at the same time? What's to stop someone from producing a character builder and a Hypertext SRD? We already see this happening. This isn't idle speculation,
it's historical fact.
Within months of the release of 4e, we had a site offering an online character builder with the functionality of the DDI character builder. Within months of 3.5 being released, we had a fully functional d20 Hypertext SRD. Again, this isn't something I'm pulling out of my vas deferens here, this happened.
So, if they went OGL with 4e, what would have happened to the DDI? We'd have more subscriptions because there are free versions available? Really? Because that's the argument you're making right now. If 4e had been OGL, somehow, despite free versions being produced within months of release, we'd have twice as many subscriptions?
Excuse me for being a teensy bit skeptical here. We never had OGL online tools because no one could make any bloody money out of it. Heck, the pay tools that we did have were minor, and the company that produced them, despite the popularity of d20, folded.
Think about that for a second - even at the height of the d20 boom, we didn't see one single successful pay offering of d20 tools. Not one. They all went belly up.
But, somehow, magically, it'll all work out this time around? What is the key element that I'm missing here? Because, as far as I can see, there's no money to be made here. We've had almost ten years for someone to make a d20 DDI toolset. But, it's never materialized. There has to be a reason.