I don't think the appeal is good, but I'm not sure there was much choice for the following reasons:
1. The $960K damages award established a relatively cheap royalty rate.
2. The non-willfullness ruling significantly limited damages.
3. There's not enough time to wrangle with potential infringers given the nature of the low damages awards. There's little incentive to settle.
4. A clear victory with large damages is needed to bring infringers to the table.
5. There needs to be a single unified ITC/NDCA decision (win) to motivate infringers.
Once the patent expires, 35 U.S.C. ยง 286 says that "no recovery shall be had for any infringement committed more than six years prior to the filing of the complaint or counterclaim for infringement in the action". As such, for every day past the expiration date it's a day that is lost forever. That being said, it won't matter if the case is lost at the CAFC.
I would imagine that the appeal will lead to a counterclaim of non-infringement by HTC.
It seems to me that this is a go for broke strategy. A loss at the CAFC would really mean the end of things. A win will mean big rewards.