SDL is an open source, multiplatform api that can deal with gfx, audio, io, cdrom, etc. Basically (for conversations sake) it wraps itself around a host oses apis. The advantage being it's typically easy to port software using it to a platform that supports it, the disadvantage being it's not very efficient, especially in it's amiga incarnations.
Ok... Understood...
But you miss the point here of the NatAmi, it's designed with being able to write programmes for it in native Motorola 68K Assembler, it would be pretty pointless in writing software for it using the api you mention as this would simply not get the best from it unlike writting in native Assembler...
You also mention that the enhanced modes (ie:32 Bit TrueColour) have been available on the Amiga for years, by that I take it you mean RTG boards, again though your missing the point how many current Amiga hardware users own an RTG GFX board, not many I'd reckon, and most likely the reason why not very much was ever written to take advantage of them...
The way I see it is the default configuration of the NatAmi would become the de-facto standard for writing new stuff for it in good old M68K Assembler which it has been designed to make best use of...
It would be pretty pointless in the designers spending so much time and effort in making the NatAmi 100% backwards compatible with the M68k series of processors if all folk were going to do was write stuff for it using the kind of thing you mention, you be as well just buying Amiga Forever and writting stuff that way...
