Ya, it is not very likely. They each make profit with their VIP hacks so they don't want to lose their independent business. Also, I am pretty sure that whoever owns T.G.S. and Dave probably are head on competitors. I would say ATLEAST 20% of the reason they don't combine is because of money reasons.

EDIT: Found out that ****** (T.g.S coder) used to be a part of MPGH, but left because he wanted some percentage of the profits of the hacks...