I have my suspicions that the Leafs are not overly worried about losing Kerfoot, unless it would be very cheap to keep him around. Similar to Holl. They are looking at guys they feel can provide surplus value going forward, such as Dermott.
If the Leafs lose Kerfoot, it will have to be a priority to replace him but they may be able to find a decent stop gap in free agency next year (Haula, Getzlaf, Krejci, Stastny, Wennberg, Bjugstad, etc.). Danault and RNH are likely too expensive. Losing Holl is also not a big deal with Dermott ready to step in to a top 4, and then having Sandin and Liljegren for a bottom pairing (plus they will likely add a good #7 and #8 as well).
I don't think the Leafs will overplay their hand too much in the expansion draft. If they lose Kerfoot or Holl, it sucks but it is not going to end them and they recover some cap space to put towards a replacement, which they should be able to find.