Andy Reid wasn't impressed with Lewis at times this past season and benched him in favor of Sean Considine and Quintin Mikell. Lewis had to look for his spots to get on the field and play his way back into Reid's good graces, which he eventually did. By the end of the season he was playing in the dime package and was seeing a little more playing time, but that's not how Lewis views his role and it's not the role that the Eagles can see themselves paying him to play in, especially since he'll want a nice raise over his $795,000 deal that he played under last season.
If the Eagles weren't deep in the secondary, things would be different for Lewis; the Eagles would be working with him on securing a deal for next season and beyond. The best thing that Lewis might have going for him is that there are other secondary mates looking at free agency - Roderick Hood, William James and Quintin Mikell - so the Eagles could throw some offers out to each of them and see which stick. It's unlikely that Lewis will be low-balled when it comes to a deal, making him the likely contender to exit gracefully.
Keep in mind that while the Eagles like Lewis, they're more enamored with Mikell and Sean Considine. If Mikell doesn't price himself out of the Eagles price range, he'll be the one staying and Lewis will exit. Lewis would likely also want some sort of clarification on what his role would be and he wouldn't be likely to accept having Considine be considered the front-runner for the starting job next to Dawkins.
The bottom line: The Eagles are perfectly happy with Considine as their starter and will likely drop Lewis. If they're going to re-sign a safety, it's likely going to be Mikell, who the Eagles believe can do more for the team between now and the time that Dawkins would eventually walk away. Besides, Lewis is going to be looking to start and with the Eagles' cap situation and the fact that they have a cheaper guy like Considine ready, willing and able to step in, Lewis is expendable.