Bad, bad, horrible.
Vast increase in rate of settlement in Georgia and the Carolinas. East and West Florida get permanent English populations entrenched before the Revolution, so they'll have colonial governments as well.
Value of labor skyrockets in the colonies, but from the 7-Years (cough French and Indian cough) War indentured servitude is right out. It'll be a decade at best before the increase is followed by an increase in voluntary immigration, so the first result will be that slave prices spike. That means more slaves diverted from the Caribbean to the mainland. The survival rate was much better in the colonies than in the sugar plantations, so the effect of the increase will be disproportionate - a lot more black slaves in North America. Plus since the islands usually got first pick, the involuntary immigrants will tend to be healthier than in OTL.
All in all, you are looking at the Floridas as real provinces (and possibly future states), a big shift of population, wealth, and influence to the southwest of the colonies, a bigger institution of slavery, and higher slave prices (which makes freeing slaves more expensive when it comes in vogue during any eventual revolution). In OTL only South Carolina and Georgia were adamantly pro-slavery during the revolution - when they represented 5% of the nation's population, and little more of its wealth. Even other future Confederate States were ambivalent, and many slaves were freed by their owners in the rush of freedom-shouting. This scenario will alter the political landscape in a manner that might be interesting, but will be unpleasant.