Multiple ADC's interfacing to FPGA
Yes, completely possible. Pick an ADC that allows synchronization of conversions, ADS1278 for example. 

You can read the conversions out from the ADCs with a single interface (bandwidth permitting) or multiple- the key thing is to synchronize the conversions themselves, and you can read out the data at your leisure (at least until the next set of conversions arrives). 

With an FPGA you will have no problem generating the proper SYNC signal (or whatever your ADC of choice requires).