If you have held off purchasing an SSD then you are a winner. The size will go up and prices are just going to keep falling, which has been the trend since 2014.
Here is an article from last year, but, 2 points are important. 1) the size of a HDD is limited to about 10TB with the current technology. The upper limit of SSDs will be closer to 30TB within 2 years. 2) New manufacturing techniques add years to the lifetime and reliability of SSDs.
http://www.networkcomputing.com/storage/ssd-prices-free-fall/1147938888 I was talking to a friend of mine who has built PC's for 25 years and he says the last half of 2016 is going to be a good time to look into purchasing SSD because manufacturers are looking to dump the smaller sizes. Any size Less than 1TB will be cleared out, because in 2017 1TB SSDs will be the standard size actively installed in new PC and sold in the aftermarket.