I don't see it. Yes, Heat will be in the mix for years. But a dynasty? Possible, but not a certainty. Leave out the injury factor, the Heat were not the best team in the East during the regular season and they were 12 minutes from not getting out of the East against an old, injury-plagued Celtics team. Think what the C's could have done simply with a healthy roster (AB, JG, CW, JO), and then consider that they came a whisker away from signing David West.
Heat were not head and shoulders above the pack in the East this year. Obviously, they can pick up FAs and strengthen their roster, but that is speculative. When they sign talented players to fill needs, then we can talk domination, but why would that be more likely to happen in Miami than in Chicago, Boston, Orlando, NY... Sorry, I don't buy the automatic attraction of LBJ/Wade -- I think the expectations, spotlights, and potential volatility of that group may make some of the better FAs prefer SA, OKC, LA, Boston, NY, Dallas, Chicago... No guarantee that the Heat will have their pick of FAs.