People are buggin out about aliens coming to Earth. Let's look at the possibilities. With the technology we have, did we find any life in outer space? No. Well, ok some bacteria on Mars that looks like something from a Lysol commercial. But that only tells us that life does have the capability to exist beyond Earth. But there are no artifacts of extra terrestrial life. So here's my belief, take with it what you will, and please if you disagree, tell me what doesn't make sense but this seems like the most logical way to go and here it is.
A most likely scenario is that they would create Von Neumann Machines. Machines with artificial intelligence that can go out and find life on other planets among other missions. They create these machines to do jobs that they couldn't do themselves. They could go on a star trek mission and travel to places where their descendents arrive at the destination. But the problem with that is, that the race may not survive and would possibly annihilate themselves in transit if not at their final destination. So instead they send a machine to get the information needed to get to other planets.
Back to the VNP's, if they send the machine out to find life, one of the requirements is to take data about the planet and what it consists of. But in order to find one, it needs to look around. we already know that it will take forever to find something with only one pair of eyes, so there needs to be more than one VNP. but there will need to be more than just a few hundred or thousand that are needed to be made and their planet may not have the resources to make so many, so the VNP will need to know how to replicate itself using resources found on any planet it lands on. So within so many years the machine will be large enough in numbers to go out and look for life on other planets.
By the time it branches out and maps 1/4 of its galaxy there will be millions, possibly billions of these VNP's and will be a very high chance that it will have created different models specific to its particular job, either a replicator, a searcher, or a data collector. There may even be communicators, machines that learns and communicates with intelligent life, protectors like transformers that may need to protect a regional VNP built to map a particular area. There are tons of reasons for why VNP's can exist in space but the overall answer to this is that there is a higher likelyhood of alien artifacts in space than aliens themselves.
These VNP's are only good to humans for the technology it possesses. The odds are high that aliens have chosen not to have these VNP communicate with us. They don't want any hostile species coming to their planet and may use the numbers of VNPs to be an intergalactic telephone line and keep the contact to that level just to satisfy their quest to find life on other worlds. They fear the same thing we do. We fear that we may come in contact with a race far more advanced than we are and come to destroy us and rape our planet. If we do find out where the alien race comes from, we may find that the civilization that found us have died out some thousands of years ago. The information contained in the VNP we may find may have an aricebo message from the aliens and their planet. That's the most we may get from them. The VNP we may find in the future will most likely not be the first generation of its kind and the computer's A.I. will be in a computer language only it and those built from the same model will understand. Not even the original creators of the VNP would understand the algorithm.
Just like the information we got from bacteria on Mars, we will only get a confirmation that we aren't alone. The only thing we can do about it is make our own VNP and survive long enough as a race to get an answer from our creation.