Like I said, maybe. If the tree really is a nuisance, then yes, If not, then no.
If he has an expert in trees that tells him the tree is normal, it's safe, etc., and yet the tree blows over in a storm, if you end in court, it's unlikely -- possible, but unlikely -- that a judge or jury would accept your opinion of whether or not the tree was unsafe over the opinion of a (presumably unbiased) tree expert.
My point about the letter is this -- if you send a letter to put him "on notice" and the tree falls, that does not make him automatically liable for the damage. If he can prove that there was nothing wrong with the tree, then it will be an "act of god" and he most likely won't be liable for the cleanup. You can't "create" negligence like this -- my neighbor has trees that are near the property line, I can't simply send him a letter and from now on he is liable should one of those trees ever fall -- there has to be some reason why they are likely to fall.
I don't know your trees, and I am not a tree expert in any event -- maybe your neighbor's tree DOES constitute a potential hazard and you do need to put him on notice -- all I am saying is that notice isn't the be all - end all. You have to have reason to give the notice.
As far as waiting to bring suit, if the tree is in real danger of falling and causing damage to your house, you could go and try an obtain an injunction forcing him to remove the tree, or otherwise abate the dangerous nuisance -- you will need to talk to a lawyer, and likely hire a tree expert to first examine the situation, and then later testify at the hearing. Whether or not this is cost effective will depend on the situation -- talk to a local lawyer or two to weigh your options.
You can't use small claims court until you have actually been damaged in some way -- you can only recover monetary losses in small claims.
That's pretty much it, unless, like I said, its worth pursuing injunctive relief.
Now, there is always the possibility that you could mitigate the hazard yourself, by trimming and pruning or whatever now, and then sue the neighbor to recover your costs in small claims -- but winning such a case is probably a long shot.
