I'm a lawyer with lots of friends who have clerked or are clerking for the federal judges from which nominees are pulled and have followed this pretty closely.
All duty/morality aside, McConnell seems to have just done something really risky for Republicans (both in the presidential election and state elections where republican governors are up, and contested senate seats). Majority of Americans think Republicans should at least hold hearings, and by nominating a pretty old, pretty middle of the road white dude, Obama sort of gave McConnell an easy way out of his conundrum. Maybe McConnell is holding out for a Cruz or brokerered Republican nominee to win the white house, but right now the odds are on Clinton, then Trump, then whatever other Republican, so it seems like he's playing with fire.
If Clinton comes in with a mandate (and it's not impossible to imagine the democrats taking back the senate this season), she can nominate as many Sotomayors as she wants.
It will really get interesting if another justice dies in the next couple months.