There's no cold wallet in the plans as far as I know. Users can get what Merit calls "growth rewards", or "growth mining", as in additional drops of MRT that vary in quantity and frequency: you get them by growing the network and holding merit in your account, curently 3/4 of each block (so 15 MRT) is distributed to the network trough PoG rewards so they are pretty generous. Of course the more (active) people you invite and the more merit you hold, the greater your rewards. I think this answers your last question too: no airdrops, as they are kinda part of the system too, but rewarding real action instead of spamming one.