The idea something can be invented by one and just one person is something belonging to fiction, not reality.
Nowadays, with globalization, research teams keep their work as secret as possible and work as fast as possible, always in fear someone would publish results "before" them (and this is the cause of several epic fails due to race to publish without cross-checking all variables; e.g.: FTL neutrinos in between Switzerland and Italy).
In past times we have many cases of "almost contemporaneous" developments independently found by unrelated teams/individuals; of course we only remember the first, but others would have got there all the same, only slightly later (e.g.: everybody (?) remember Lobachevsky, but few know about Bolyai's work).
There have been real precursors, inventing something really ahead of their times, but they invariably died swimming in ridicule, only to be "rehabilitated" and brought into the spotlight of scientific fame much after descending into the grave (e.g.: Galois and Mendel).
Of course nobody can really know what would have happened, but it stands to reason technological situation was ripe for Tesla's work (as testified by immediate acceptance) and thus those "miracles" would have been performed by someone else very soon, had not he arrived first.
This, of course, has nothing to do with complottist view of Tesla's life and death. Whoever (if true) manipulated his work would have done the same with other researchers and result would have been similar.