The biggest problem which you should consider during porting - many components still not there in M1. Check readme-ui.txt in order to check the full list of them.
But good news - if you have more betas on your way you could update 4.x smoothly between them to get new components as far as them will appears. We switched to timeboxed releases (4-5 weeks before every next one). So new components/features and stabilization issues fixes will be officially released pretty fast(comparing to 3.3 when we had about 2 month's release cycle)
But if you need to deliever application in short time after beta - probably you should use stable 3.3.x with upgrade in future.