Electric airliners are at least two decades away.
Energy density in batteries is just not where it has to be to sustain even regional airliners, much less the long haul voyages that Airbus and Boeing are chasing after in their newest jets, the 787 and A350.
Aircraft design and certification is a slow and expensive process, a process I see Musk getting bored and/or irritated at. Moreover, they'd have to get airlines to bite. This is where the tricky part is. Whichever of Musk's companies builds this electric airliner has to match the reliability and service of Boeing and Airbus, whose newest planes have a dispatch reliability of >99.5%