Aircraft performance is not the only relevant factor when considering 146 replacement. A 146 capital cost is just a fraction of the capital costs of a 717. Even if 717 has marginally better payload / range, if this costs you 6 times what the 146 does, how do you justify a change of aircraft? Who pays? The company / the pax?
Many people knock the 146 and demand for replacemement - but I would like to see real justification. The aircraft is old? Compared to what, on what criteria? Cycles, years? Reliability of this type is actually improving.
Regional airstrips are often short with hot temps, the 146 handles this like no other I am aware of, and does it very cheaply, with large cabin comfort, unlike the CRJ, ERJ. Incidently, the CRJ and ERJ also have capital costs several times that of the 146.