I know this isn't going to be a popular opinion, but the chances of TASCAM doing anything here are next to nil. They no longer make the dvice, and any future sales are going to be back inventory of stock they've already moved to external vendors. So they have no financial interest in 64-bit drivers. The existing 32-bit drivers work through Snow Leopard, and if they release new 32-bit drivers for Lion, they'd need to do back-compat work for all of those OS releases. Again, no win for TASCAM.
They provided a device which supported all Mac OS releases through the time of the device being sold (2009) up to two years later. From a vendor point of view, there is no obligation to follow the customers if they choose to upgrade to a new OS. And while Apple may bend over backwards so Lion doesn't look like a new OS to customers, from the kernel point of view it's a new OS. Especially with the shift to a 64-bit default.
So don't expect TASCAM to budge. It not only doesn't gain them anything, it's a net loss for them to issue new 32-bit drivers, posibly breaking existing customers on Snow Leopard, or issuing 64-bit drivers, possibly cutting into sales of new hardware. When we bought into LIon, we made a choice that TASCAM was not bound two two, or five, years ago when we bought our FW1884. And from the busines side of things, it makes absoutley no sense for them to ever touch those drivers again, regardless of how much we want them too.
I've moved on to a new interface (Focusrite Saffire Pro 40), using the FW-1884 as a mixer. No glitches, no problems, 64-bits. I'm much happier now. Although if you're looking, I think I'd maybe have gone with Mackie Onyx for a bit more. Yes, I put a lot of money into the FW-1884. And now I can't give it away on eBay. That's hardware. Buy quality, use it, upgrade only when you need to. Mostly important, make art and have fun.