[therein]

But aren't there massive gaps where an intermediate celestial body to perform this jump on will be simply too far away for traditional space travel?

[jessriedel]

Probably not. On the timescales of millions of years, the only thing that really matter is whether it's physically possible, and it looks physically possible to colonize other galaxies.

http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spr...

I'd be pretty surprised if the jump between galactic groups is much worse.