As regards stone-fruit trees like plums,peaches etc, the unusual weather has made these trees to remain dormant longer. I'm refering to my country which is Malta. It might be also the case to countries with colder climates.

It could have died ! Sorry ! try scraping some of the bark away with your nail to see if it is green underneath. I had a dead pear tree myself once, it never got leaves and eventually I gave it up for dead, however I'm no expert!