I'm in a similar boat- I'm planning on offloading a bunch of old McFarlane DC figs, but mostly the ones I bought on a whim or back when the line started to support it. I'm still keeping plenty, and happy to. For all my frustrations and shit that I give Todd, he does make good figures more often than not, and I'm happy to have them on my shelf.
Much as I love Mattel, and hope they make good product, there's definitely things I don't see them doing as well as McFarlane. Some things they'll probably do better, but it's a give and take. Really, it's all gonna come down to look and feel for me. As with McFarlane, it'll be a case-by-case basis; is it a character I love? Is it a good representation of said character? Is it a decent value for what you get? Etc. etc. I don't need stupendous articulation or a sea of accessories with every figure. Would it be nice? Sure; especially as far as accessories are concerned- I certainly like having the option to use them, but if I'm being honest with myself, most of the accessories either go unused and sit in a bag, or get holstered on the figure if possible to add to the overall look.
I, like many others, am gonna be collecting until the day I die, especially Batman related things. If we're getting down to brass tacks, as long as the product itself brings me joy, I don't really care about articulation or accessories or whatever, no matter how much I may convince myself I do. Some of the old glorified statues bring me just as much joy as the hyper-articulated offerings. So will I get every single one of Mattel's offerings? Of course not, just like I didn't get every one of McFarlane's, or Mattel's before that. I'll pick and choose, and as long as there's still passion and love put into the product, I'm sure I'll happily keep supporting. At this point, it's mostly just curiosity to see how they'll look, what prior ideas they'll implement, and how they'll stand on their own.
Anywho. Was nice to watch the full NYCC interview above. Regarding Nicholson Joker, at least Todd seems aware of both his restrictions and his options. If nothing else, he does seem the kind of guy who's willing to just go knock on Nicholson's team's door and ask for the rights. They've obviously approved figures before, so it's not out of the question. I hadn't even thought of him doing something like what he did for the 66 Batgirl, and doing Nicholson-esque rather than a straight likeness. Not sure how I'd feel if we got something that looks like him but isn't him. I'll have to think about it.