If emulation never picked up then the pace at which new hardware and consoles come out now would be slower.
I don't know in what sand your head is, but it is more the opposite. Emulation goes twice as fast as hardware development. The fact that there are no XBOX 360 and PS3 emu's are that these machines are bloody fast, and there is no good overhead available on the average computer. Remember these 2 machines use PPC code, and so the overhead needed is quite large.
Another issue is that there is a certain unwritten law to not emulate current profiting systems. PSP, PS3 and XBOX360 are still sold, and emulating the PSP for example on a iPad would cause a lot of legal trouble. If PSP is EOL somewhere in the next months, an great working emulator is just a few weeks away.
On the positive side: the hacking-community reacts to new hardware blocks within a few days, and cross emulating systems is the new hobby. Android running on iPhones, Linux on iPads, MAME running on Nikon D3 camera's, you name it, and some home-brew hacker finds a way to get it working. Have a look at MESS. It almost emulates every computer ever made, just with a tiny 100Mb of code! That is just flabbergasting!