Allegiant is slated to be all Airbus by August of 2019 according to the last official news.

To give you an idea of how 2017 is shaping up-

2017 will begin with 33 airbus' and end with 53.
IWA will be all airbus by summer 2017
PIE will be all airbus by fall 2017
AVL will be all airbus by winter 2017

SFB and LAS will begin their transition in 2017 but will not complete it until the end in August 2019.

The rest of our bases are already airbus.

Our projected aircraft totals are as follows
12/2016 - 85
12/2017 - 91
12/2018 - 93
12/2019 - 99

It would not surprise me at all to see these numbers grow much more. The company is opportunistic about their growth, when they see a good deal on something they tend to go after it.