So solely taking the "accentuate the positive" approach:
1) Without the OGL/SRD, it's very likely that people will work out that they can make very D&D-like RPGs without problems. Either will sue one company, maybe take them out, but will be forced to show the hard limits of their IP (copyrights, trademarks), or WotC will be too afraid of that and associated extreme bad press (which wouldn't be a one-off it'd come back every time something happened with the case - it'd basically be the OJ Simpson trial but for D&D, and people like io9 would probably be reporting on developments/arguments weekly), and definite loss of some copyrights/trademarks, which will essentially show people can do what the hell they want so long as they stay away from the most obvious WotC stuff.
This will free up the 3PP market in the longer-term.
2) ORC will probably become the default share-alike licence for TTRPGs, and will actually be protected, unlike the OGL.
3) People will increasingly discover RPGs outside of D&D. I disagree with anyone saying this isn't a long-term positive. In the short term, it might be a negative, but in the longer term, it'll make RPGs much more likely to survive as they'll be diverse. If say, 40m people are playing RPGs now, and 30m of them are playing D&D, then even if say, only 25m people were playing, but they were playing a much more diverse selection of RPGs, I think it's more likely that TTRPGs would continue exist in a real way in say, 2040 or 2050, than if the 40m situation, where it's very possible D&D would basically vanish for some reason or another (not least some kind of boneheaded decision by whoever owns the IP then), leaving a lot of people really scrambling in a way that is likely to see a lot more of them fall out of playing RPGs.
Destruction of d20 die as primary generator of RNG.
Yes let us pray.
Not many of us praying for this but good god I wish it was gone for everything but combat/saves at the least.