LMAO. If by "big" you mean that it will wallow in obscurity until it eventually disappears a la the Tapwave, then I take your gaurantee as gold.
If by "big" you mean that it will be remotely successful or that you will ever actually see one in the wild without buying one yourself you're out of your mind.
Tapwave stiffed because of it's DRM restrictions and high price. It was a PDA masquerading as a game system. Emulator authors stayed away, and so did the public. Good riddance.
The GP2X seems to have quite a bit of momentum behind it if you are looking for a handheld emulation/movie/MP3 machine. No commercial games at all probably, but with two 200 mhz CPU's, 64 MB RAM, SD cards, Linux and what should be near perfect SNES & Neo Geo emulation, it will be worth the $200 price point.
And "success" is relative--if I never see it on the store shelves in the U.S. but I can easily buy the machine online and have access to a huge amount of free emulators and freeware games, I would still consider it a success.