That was so almost my new wallpaper... As for Gurren Lagann, it's Bandai Entertainment doing the sub only release. Bandai Visual are the ones releasing Macross F in Japan, and they're already no strangers to sub only releases in the U.S. SRW, Gunbuster, Diebuster, and several others have all been sub only releases. The trick is in getting them to bring F here period.
Supposedly the big hault on Macross being released over here (according to HG), hasn't been HG themselves, but Big West being wary of working with R1 companies (due to Tatsunoku & HG). But given their great relationship with Bandai Visual, I don't see how they'd refuse a license from them.