With the possibilities steaming towards us regarding rate/cost/capabilities in launching stuff, NASA -and associated subcontractors- will have their hands full developing new technologies anyway. Heat shields, landing systems on other planets, radiation shielding, base building techniques, space stations, comms...More than enough to do to keep jobs going. So there's no need for SLS as a launcher, and no need for the SLS project jobwise (in the broad sense, not just the job but also the related knowledge etc)
With sufficient thrust, water towers fly just fine.