They will marry and with probably less thought and restraint than hetersoexuals at least intially. Whereas heterosexual unions have developed various norms and practices over the centuires that attempt to get the partners to look realistically at their prospects, gays don't have the same culture to fall back on.
They will undoubtedly commit more readily than hetero's both because the culture isn't their to provide guidance and because their will be tremendous presue to be the first to join the bandwagon.
The fallout will be overburdened courts to handle the the volume of broken relationships. They will not only tax the court systems they may influence the outcomes of heterosexual property splits and custody battles. It will be interesting.
So, all in all I disagree. The aspect of divorce will not be a cause for gays to avoid marriage. In fact in a queer way, it might encourage it so that some gays can say they were divorced like their hetero friends,
I do agree however, that legalizing gay marriage is a step in the wrong direction, but firmly believe too, that if it occurred, it would totally backfire on the gay community because it would give them what they've fought for and yet, by and large, none of them actually want to make that type of commitment. So the ability to marry is virtually mitigated by desire.