In general, the family of Coronaviruses mutate/evolve slower than influenza. That said SARS-CoV-2 is new, we don't fully know it and we can only assume it is going to behave following that pattern. It seems to be somewhat better at propagating than common influenza (2x?), which is no slouch in that regard.
There is no immunity. Vaccines and antivirals do not work with SARS-CoV-2 (if laboratories had kept onto researching on the 2003 SARS virus and produced a vaccine the latter MAY have worked to some extent, but as it was the epidemic was contained investigation stopped, sad). So we've got to wait for a vaccine for quite a bit of time.
The death rate is reportedly between 4 and 50 times higher, but we need to take this with a grain of salt as the amount of unreported cases (many of them asymptomatic) may be huge (thus considerably lowering the death rate, possibly one order of magnitude).
Hopefully after one, two or three infections, immunity can be acquired passively, and although becoming endemic, the virus may turn to only affect children in a very mild way until they acquire immunity to the virus (and hopefully to similar viruses from the same family).