The B8 generation of Audi products are nearing the end of their lifespan and with them the 4.2L FSI is as well (except for possibly the next R8, though even that I somewhat doubt).
The next generation RS4 and RS5 may or may not move to a 6 cylinder engine - we don't know yet. But they will, with near certainty, not be powered by a naturally aspirated engine.
2008 Interlagos Blue E93 M3 - M-DCT
2011 Salsa Red Jetta TDI Sportwagen - DSG