The Summits have not been discontinued.
There is a V2 coming out with the new and improved(?) crossover used in the Spire. We shall see if the V2 is better or not. $2K seems a bit much for a crossover upgrade but what the hell do I know.
The Spire MAY have a cleaner, more transparent midrange. Again, that remains to be seen.
In theory, the Summit should have and probably does have a better defined lower end assuming they are properly set up with the xover volume set correctly, given the fact it has two (2) woofers / amplifiers per speaker versus the one in the Spire.
Less weight / body in the bottom octaves can and will, in some setups, make a transducer sound cleaner and more transparent in the midrange, all other things being equal.
The new list for the V2 Summit is $12K for the basic model.
GG