@DStastny
it's a fair point. when i decided to get a next-gen amiga back in 2009, i wasn't able to get new hardware then, either. acube had sold out of their SAM440-flex boards just like they've sold out of SAM460 boards and A-EON has sold out of X1000 systems these days. so i purchased a lightly used SAM system instead. i saved money, and loved it.
there are rumors the X5000 is just around the corner, but if that will be too costly in any case for you, i highly recommend watching the classifieds on amigaworld.net, amibay, and elsewhere for opportunities to purchase a used system if you're still interested in purchasing a NG machine.
if you just want to try it out, go for the UAE route as kamelito suggests. it's not officially supported, and it has a lot of limitations (including performance), but it can give you an idea of what AOS4 is like and you can use it for coding. my UAE instance, for example, is primarily to run codebench.

-- eliyahu