Interesting story, but I am not sure that Ted Lilly is a completely analogous situation. They are both veterans about the same age at the time they will be traded, and in their last year of the deal. They both were owed about 10 million for the final year. That is where the comparision ends though.
Ted Lilly was at best the third best SP available on the market (depends if you want to count Roy Oswalt as available since he a NTC and could steer to whatever team he wanted). Ted Lilly was a respectable 3-8 3.69 with the Cubs last year, but there were a lot of negatives on him. His velocity was down for most of the season, and his July ERA of 5.34 certainly didn't add to his value.
We don't know exactly what is going to be on the market, but I am not sure if there is going to be a better slugger available. Carlos Pena after not hitting a homerun in the month of April is fifth in the NL in homeruns. He has batting average up to .226 for the baseball dinosaurs, and has been one of the hottest hitters in baseball as you pointed out.
Now Pena could fall off the cliff again since he is known to be a streaky hitter. And I don't know what the market is going to be like, but I see multiple teams that have a need at 1B/DH that will be in the race. Diamondbacks and Angels are teams that a lot of people throw out. I think the Giants would make a lot of sense as well as anemic as their offense is. A scenario that is interesting to me is a deal between the Cubs and Pirates that involves swapping Pena for Overbay and nets the Cubs a top prospect or two. In that deal, the Cubs would get a guy to fill out 1B for the rest of the year if they felt that was an issue, and a guy that is a pretty good glove at 1B since I think they are concerned about Castro's confidence on defense. If the Cubs picked up the deferred money, then it would be an even money swap and an addition of about .150 OPS to a position.