300ppi at 4.5in would probably be 720p - that's what the First and M4/One mini have at 4.3 in for something like 330 ppi. That would be m y guess anyway.
I'm more concerned with the promise of 4GB ram and 128GB storage. That's going to be very expensive. The highest end phones today cost more and half half or less of that. (I know, things get cheaper, but this isn't orders of 20 million, it's orders of 20,000)
Not only the ram. The 'sapphire screen' and battery are probably going to be the most expensive pieces of the system. I don't think anyone is complaining that their gorilla glass screen is not durable enough. The highest end phones have less ram most likely because of battery life issues. That ram has to be refreshed, and more of it means more drain on the battery. Not to mention that in android phones, they try to fill up the ram as much as possible to avoid accessing the flash storage after booting since that also drains the battery. The consequence may be longer boot times, if Ubuntu does this also.
128gb of flash storage is like $150 retail, probably less in bulk. 4gb RAM is not expensive, yeah it's integrated, but the reason why device manufacturers hold back is they're penny pinchers who are looking to maximise profit, and they're also running mobile OS'es that don't need 4gb.
I'm more concerned with the promise of 4GB ram and 128GB storage. That's going to be very expensive. The highest end phones today cost more and half half or less of that. (I know, things get cheaper, but this isn't orders of 20 million, it's orders of 20,000)