I could see Francisco getting significant playing time this season. As a LH hitting 3B and LF, he fills several needs for the Reds.
1. Rolen will almost certainly miss a lot of playing time, and that would be best if he is going to be healthy at the end of the season. Cairo is the only backup right now, but he has a lot of mileage, and could easily fall off from last year. If Francisco can get this throwing together and more consistent, he has the potential to get some starts at 3B against RHP.
2. Francisco could be a better ption in LF than Lewis as a LH hitting counterpart to Gomes. Francisco could fill the role of Lewis while also acting as backup 3B.
3. As a pinch hitting LH batter he would be the best Reds option off the bench when not starting.
Of course the question is whether his defense in LF or at 3B is good enough on the MLB level. But Lewis and Cairo are not defensive whizes either, so why not go with the younger better upside player? I say keep Cairo as insurance and use Francisco in place of Lewis as the 5th OF/ backup 3b.