Let's keep in mind that Dream themselves provide that 13MB bank - and no higher-quality alternative AFAIK, this is what they license with every chipset sold out there.
The fact that the chipset supports 64MB doesn't necessarily mean that 64MB should be fully used to achieve the best quality - take for example the SC-55 rom: it's just 4MB.
GUD is not ready yet and it takes really really long time to organize samples, set loop points and other bazillion variants to make it sound good/correct. I've helped with testing last year and I can confess that it's not an easy job - and all I had to do was to test the banks during playback , nothing close to the technical stuff that is behind creating it. It's far beyond sticking samples with more resolution and have it work, everything must be painstakingly handcrafted and tuned in order to get decent playback out of it.
As to the X2 expectations - not aimed at anyone in particular here or trying to start a flamewar - there are various samples provided on the sales page for the available banks so I assume one liked what he heard and then buys it or not.
Is there room for improvement? Sure and that's why the GUD bank was created but surely this must be considered as a bonus when it comes and not as something that is expected 101% to happen in a preset amount of time, the fact that there is work undergoing on this alternative bank pretty amazing by itself IMHO.