Depends if you really think that would put you over the top. And how long term the Jones injury could be. Really tough call, not sure what I would do.
I don't really think there is any long term injury concern for Jones. And I think Spiller, even if he doesn't have a great season this year, is likely still a higher pick next year than Jones would be. I mean even if he falls back to about the 12th or 15th RB he's probably not too far behind the #3 or so WR is what I think Jones would likely be next year.
We start two WR, two RB, and a flex. I've also got Dez Bryant, LeSean McCoy, and Doug Martin as my keepers. Have Antonio Brown as my now WR2 and Knowshon Moreno as my Flex. And I've got Percy Harvin waiting to come back from the injury. Picking up Spiller now would put him into the lineup and Knowshon onto the bench aside from bye weeks. I'd still need another WR for when Brown/Bryant are on bye or if Brown ever has a really tough matchup or starts to struggle (Dez is obviously an every-week guy).
I'd love the trade if it was for Graham, as TE is a weak spot for me (Cook), but that's nott gonna be on the table. I think Spiller is by far the best player I could acquire, as he's still a great keeper for next year and only one guy in the league that is really out of it looks to be willing to do that type of a move for an injured Jones. The other bottom dwellers have guys like Cobb, MJD, Nelson, V. Davis, Sproles, Cruz, and Gore. None of those seem like nearly as good of keepers for next year as Julio to me.
I think I gotta pull the trigger and then just hope that Spiller gets back to the promise everyone thought he had coming into the year (I drafted him #3 overall in one league) and that Jones remains just a stud WR instead of becoming the no-doubt #1 guy like Calvin Johnson is now.