Safeco Field lessens his value. It lessens every bat's value. It makes pitching easy to come up with though I suppose. I personally believe Ellsbury's season was overachieved and don't expect this sort of performance again. Hell, he posted a negative WAR last season (though I would also consider that a fluke). I think his true value is somewhere in the range 2-3 WAR. Whereas I, trying to be totally realistic here, view Felix's true value somewhere in the range of 4-5 WAR.
For comparisons sake we'll take the last 4 seasons of Ells' WAR (leaving the first one off because, hey, rookie.) He had: 3.5, 2.1, -0.3, 7.2. That represents his age 24-27 seasons. Felix on the other hand had 4.5, 5.8, 6.2, 4.7 in his age 22-25 seasons.
I have to think that Ellsbury doesn't look all that attractive to the M's and IMO Ellsbury
EDIT: He also had decent positive WAR numbers for the two years leading up to that.