20-Year Prospect
It seems pretty unlikely that toys are going away any time soon. There are more kids on the planet than ever before, and they still need to be entertained by all the creative things designers can come up with. The growth in the industry might be slow (source), but you can bet we'll still need designers in twenty years to think up new ways to make kids happy.
That said, it'd be a smart move to embrace the technological changes in toy-making. Most design is done on computers these days, and the objects being created are more sophisticated than ever—if they're even objects, that is.
The growing market for digital apps might encroach quite a bit on the toy market, so make sure you're staying attuned to the technological climate. You don't want to be building wooden toy trains if there are going to be hover boards and flying cars sometime soon.