Hi I have a slightly souped up Amiga 1200 nothing special just a few small upgrades that make it run os 3.9 brilliantly so why was there nothing after, that may have been really good and still worked on a slightly upgraded Amiga 1200 .
Simply because it wouldn't be profitable. Look, if you already compare the money I got from Os 3.9 development to what a software developer would get on the market for writing PC software, then this was really a joke. I did it for the fun of it, not for the money. Os 3.9 sold, but given the number of copies it sold it was barely worth the trouble for anyone, including the company that organized its development, namely H&P. Os 4.0 came after 3.9, and the scheme Hyperion seems to be using (as far as I can tell) is to make at least some money on the hardware to finance the software development. Funding a company from Amiga software alone wouldn't simply work anymore - the community is too small, and is not willing to spend enough money on a new release to make this viable.
The only way how this could work would be to use a different development model, probably some open source type model that would give interested parties free access to the sources, plus probably a test farm and a centralized repository, probably with some official net-based releases from time to time that have been verified and tested. It seems, however, that Hyperion (the current license owner of Amiga Os) is not interested in this model - likely because it would compete with their Os 4 development, and hence would diminish their Os 4 sales. I understand and respect this, but it also means that we're trapped with either outdated software, or private hackery based on inaccurate information on how AmigaOs is working - pretty sad, but that's reality.