Bethesda has never been against bringing out portable versions of their games, even though they dropped Oblivion psp. But I think theres a good chance for this happening and I would like see it happen.
I could be wrong but I believe climix, the company developing the Oblivion PSP game, was severely downsized (which resulted in a number of games being cancled.
As for a mobile Fallout game, with the exception of the Oblivion PSP game all of the TES Travels titles were developed by Bethesda's sister-company, Vir2L. I'd keep an eye on their site for any news concerning this. I doubt they'd port the original game, but they might develop one of their own.