At the moment the price of XEM is really pure speculation but that was no different from NEMstake from June 2014 to March 2015. . I think NEM's mobile client is coming out in a week or weeks (...months?) but, as awesome it could end up being, I don't think it by itself will send XEM into the stratosphere.. because there's already some alts with mobile clients and it's not really a huge wow factor.
In terms of speculation I'm only really seeing:
1. NEM has to avoid hacks / thefts and then it can promote itself as being the safest / most secured crypto currency (due to Cosigning, Eigentrust++, et al). Yes exchange theft can be prevented if they all implement cosigning with funds.
2. AltNemo / Ecosystem has to take off
3. User adoption (which will probably be the result of the above two, plus some marketing).
There's also always the scenario that the Chinese come in and pump (like they did with NXT, BTS, et cetera) but that will only send a coin to around $60-$100 million and what goes up must come down.. and it doesn't goess well for a coin's reputation if people get burned by extreme volatility..
Volatility is inevitable. You just have to fight through it. That's crypto.