Yes, going from 1024x768 @ 132ppi in the iPad 2 to what the iPad 3 is going to have will seem a big jump... but mainly because the iPad 2's resolution sucked, not because the 3's is so much better than the resolutions/densities available on some Android tablets.
Uh... no. To put things in perspective:
1280x800 @ 10.1" = 149ppi
1920x1080 @ 10.1" = 218ppi
1024x768 @ 9.7" = 132ppi
2048x768 @ 9.7" = 264ppi
149ppi vs 132ppi = 1.13x (13% sharper)
264ppi vs 149ppi = 1.8x (80% sharper)
264ppi vs 218ppi = 1.2x (20% sharper)
It's a massive jump. 80% sharper than the current standard Android tablet, and 20% sharper than the next 1080p tablets that will come out. If you find 10.1" Android tablets having better resolution than the iPad 2 with only a 13% difference in pixel density, imagine the difference of 80% compared to the iPad 3, or 20% between the iPad 3 and the upcoming 1080p tablets.
If you want to bring 7" into the mix...
1280x720 @ 7" = 210ppi
264ppi vs 210ppi = 1.26x (26% sharper)
So it'll be a massive jump regardless of what screen you look at. Numbers don't lie.
To match the iPad 3 in pixel density, Android manufacturers will have to look at 10.1" screens at resolution higher than 2240 x 1400, or 7" panels that are around 1600 x 1000 in resolution. It's arbitrary because there isn't any standard resolution around there.
However, Apple can still nicely scale to 330ppi on current iPhone-level Retina Display by moving to the next standard 4:3 resolution of 2560 x 1920. I'd imagine such a move to be a nice upgrade from the iPad 3, if and when Apple decides to do so.