As for Serpent, what does that mean? I don't get that at all. You should trade him for Decker or Brown now because in a few weeks you will value him too much to trade for one of those guys? That sounds like getting the most out of your invesment...
If you want to move him at all costs, like OP does, because he thinks Spiller's value is at its highest now, you have to trade for players that were mentioned because it's doubtful he can fetch much more. Unless it's to the people in this thread, but even then they probably won't actually trade much for him, or they already have him.
If he does pan out like you want him to, then his trade value goes up, so you can demand more, but then you won't want to let him go for anything less than top value, which again you'll have trouble getting because nobody is going to just trade one of their foundations to maybe fill a hole and just create another one.
So again the only way a trade really works is if it's two mid-level guys that fill some sort of depth issue (i.e., Team 1 has 2 WR2s and Team 2 has 2 RB2s, so they swap one for one) or someone takes a hit on perceived value (i.e., one person has a player projected at RB1 the rest of the way, and trades him for another player's RB1, but both guys actually consider their own players the RB2s, this is rare).
But nobody is likely to trade a Megatron for an Arian Foster, even if the point totals were exactly the same you are not going to replace that production that you give away at the position.
The people here that are insisting Spiller is going to be a top 5 RB but that they can turn around and trade him for top 5 talent at other positions are not thinking things through imo. Either Spiller isn't going to be a top 5 in their eyes or they're going to have to trade for less, but even then who trades a top 5 RB away.