Don't underestimate Madrid's muppetry. They sign players for the sake of it even if they're not needed, anything to placate their ADHD fans and board members. Bayern are also an option - Yes I know Vidal has suggested he'd only move to England or Spain but I think Guardiola is a big fan and now that they've more or less sold Kroos he might try and entice Vidal.
I don't think Guardiola's a big fan at all - Vidal doesn't seem his type at all, he's not a passing tidy midfielder operating in tight spaces making 150 passes a game but a box-to-box with lots of energy and desire to make things happen. Besides Vidal has said that he won't join another German club out of loyalty to Bayer Leverkusen back in 2010 or 2011 when Bayern wanted him and he went to Juventus instead despite them being significantly weaker at the time.
As for Real Madrid, I think they'll tie Kroos up in a matter of a couple weeks and then move on to the next flavour of the month - Rodriguez - to replace a perfectly good Di Maria as well as look for a forward to replace a perfectly good Benzema. They're not going to replace Modric with Vidal IMO.