Falcons sign Mariota to 2 year deal

There is no gamble. The decision was made by the front office. The falcons are in full rebuild mode. The fans and everyone in the front office knows it. They traded away the best player in their franchises history at the most important position in football and signed a veteran stop gap with upside.
The gamble is trading the known, proven commodity (Ryan) and going into the unknown.
There's no guarantee of getting a next level QB in any draft or in FA next season.