Dye and NPS (and ICD and Eclipse for that matter) came to a settlement because it was cheaper than fighting a lengthy patent case. Simple as that.
It remains to be seen if WDP will "see it through" - AFAIK they have not had the dodgy patent waved at them yet; what they have done is wave some irrelevant patents of their own towards SP as a threat. (Irrelevant because they quite clearly don't apply to any current SP product.) Think of it like a nuclear deterrent - everyone knows that the actual cases wouldn't go anywhere, but the threat of it costing the other company lots of money to fight it prevents both parties from pushing the issue too hard. Thus the issue is at stalemate between WDP and SP, and each company carries on its business otherwise unaffected.