Richard, I must first tell you that I am not a professional when it comes to plant science and breeding. I do like to dabble in it but I don't have all the answers, but I will try and answer your question. The reproduction process that the Lord distilled into all seed it quite remarkable when observed. That is the #1 thing a plant is programed to do in most cases, reproduce after its own kind. Some times you can pull a plant and yet watch it try its hardest to send out a seed head so as to produce more seed.
Hybrids are a cross between two or more varieties to achieve a certain outcome. Now how they know what the outcome will be I don't know, but the plant breeders somehow know. They usually are looking for certain characteristics that they think will enhance one-another when crossed. Oftentimes they will cross one with like good keeping ability to one with good appearance for instance. They mainly look for decease resistance, productivity, production, size, uniformity, and taste. Like with tomatoes, they have thousands of varieties at their disposal, to mix and match as they see fit.
Most often when you cross two varieties and the genes themselves are mixed, the first offspring or the F1 seem to in most cases to have a lot of vigor, which is what the breeder was wanting. Within the F1 seed we find a certain amount of genes from one variety and the other kind of like locked together to form this new variety.
But now if you were to plant the offspring of the F1 which would now be called F2, some amazing things good and bad can start to happen. These genes begin to unlock so to speak and start rearranging themselves at random. So now you plant the seed of the F1 fruit which we now call F2; and I must say here that the F2 stage is the most amazing to me to watch for with all the genes starting to unlock and rearrange themselves, you don't know what you will expect to see. You might have different colors, different sizes and shapes make themselves known. You will see differences in vigor, decease resistance, production,and yes taste.
Now out of one F1 variety you have just opened up a can of worms so to speak. For now you have the potential to create multiple segregates or future varieties out of just one. To illustrate this, I had a tomato breeder send me a pack of F2 seed this spring to evaluate and see if anything interesting would become of it. I got 12 plants to come up from that pack of seed and from the 12 plants, one was purple, one was chocolate color, some were yellow, and a couple were orange. A few more were pink and red, while I even had two that were GWR (Green When Ripe). Of all these different colors I had several shapes. Some were big beefsteaks, some were medium slicers, while others were hearts. And I could go on about vigor, taste, and disease resistance. But all from one pack of F2 seed.
It would take at least 8 generations for all these genes to settle down and for what could be dozens of new varieties, for you will see some variation in the F3 and even farther. So yes to answer your question, no you will never have true reproduction of the same variety as you knew it, for it will now transform its self into a combination of the two using a variety of the many genes in the two parents. Like i have said, this is the process that has taken place naturally and unnaturally since the beginning of time. this is why we have such diversity in everything we see in Gods creation.
This whole process has taken place in countless gardens ever since man has began gardening. Now would I advocate planting hybrids? No not at all. For until the genes get settled down, the plant will not be able to pick up all the nutrients it could otherwise. Don't ask me why, but research has shown that this is what happens. So if we were to grow hybrids all the time, our nutrient content of our produce would be limited, and we know we need all the nutrients we can get. And while on the subject, if your soil does not have the nutrients in the first place, it won't matter if you plant open pollinated or hybrids.
Hope this doesn't make more questions then it answers, God bless Mark.