Dont know much about Gas engines (yet ), but I suspect that it is only really a time issue. Gas powered large planes have only really taken off in the last five years or so, with mass production of both large kits, artfs and dedicated engines for them. Prior to that gas engines were converted from existing engines (strimmers, lawn mowers etc) and the planes were mostly special builds.

2 stroke is simpler technology, but given another 5 years I'm sure that you will start to see 4stroke gas engines built light for model aircraft, and we will be discussing why no one buys DA50s any more, but gets XYZ 75cc 4stroke instead.