The next T-Mobile myTouch, which looks to be a fine phone as T-Mobile's first video-chatting Android phone, is being re-branded as the myTouch 4G. But it's not really 4G. And it's pretty lame of them to call it that.
The myTouch, along with the G2, are T-Mobile's first phones to run with the HSPA+ networking standard. While you can jump headfirst into the technical details if you'd like, simply put, HSPA+ is 3G. It's very fast 3G, but it's technically a 3G technology.
T-Mobile's using phrasing like "4G speeds" and 4G branding because right now, where there's HSPA+ coverage, you can get download speeds that are definitely on par with WiMax and that match the lower end of what Verizon's initially promising for its legit 4G LTE network. (There's some geek-level dispute as to whether WiMax is truly 4G, but most people consider it 4G at this point.)
T-Mobile's prudent for pushing ahead with HSPA+. It's much cheaper and faster to upgrade existing networks to HSPA+ than rolling out brand spanking new 4G networks (as you can see, since they're already launching it, while Verizon's only going to start launching LTE this year and AT&T won't jump on it until next year). And the real world speeds, for now, are pretty comparable to what you'd see on existing "4G" networks. But it really shouldn't be trying to actively confuse consumers. Tech is tricky enough as it is without wilful misdirection. [T-Mobile]