First of all! Best wishes for 2015.

MySQL is capable of handling moderate sized databases. At this point, I would not recommend going to Hadoop at this point. The problem with MySQL is that it locks the table when it does an insert operation. NoSQL databases do not have this property, but this is at the cost of structure of the data etc. Have a look here: http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis

Did you tune the parameters of MySQL. By giving MySQL some more memory, and loosening some of the parameters, MySQL is quite capable of handling quite some data.

A wizard can be found here: https://tools.percona.com/wizard. First, try the config on a test-database.