is it possible to have one wallet for multiple cryptoccurencies 
I think there's a few prototypes around, I'm not sure anyone has an actual good solution to this. Technically of course yes software can be modified to follow multiple blockchains and track addresses for each independently, however:
* Bitcoin Core is maintained by the Bitcoin developers, who have minimal interest in supporting altcoins. I know of a derived implementation that's working on multicoin support, but it's unclear to me how they'll stay up to date with Bitcoin Core security updates
* Multibit HD could be modified more readily to support altcoins by combining bitcoinj with libdohj, but as far as I know their devs have no interest in going multi-coin
* "Android wallet" I've talked to the developer for, and they have no interest in multicoin support
* Electrum has always been forked to support coins, to date at least
I believe Ledger are working on it, one of the more recent hardware wallets in theory supports Bit, Lite & Doge, but that's about it. I'm guessing also that you want support for the more esoteric alts, not just the top-5/top-10, in which case no, there's really nothing because 90+% of them are unsupported stuff someone released and hasn't worked on since. Also, what's the motivation for a developer to work on a new wallet?
