IluvTTATT asked- Do you think the Lenski experiment will have some other evolution in the next twenty years? Is there anything that can be done to "speed it up"? Or would that violate the "rules of the game" in that it wouldn't be "natural selection"?
Well, it's not "natural selection", since the scientists are controlling the environment, feeding some colonies different solutions of maltose, citrose, etc. 'Natural selection' is when no one other than 'nature' is controlling the process, so the experiment is more akin to 'artificial selection', except unlike dog breeding, they're likely not picking for certain traits.
I suppose they could, and you'd better believe that in the past there were germ warfare labs around the World where studies were done on weaponizing viruses and bacteria to make germ warfare a possibility, increasing virulence to make the critters easier to pass to others, but not so deadly that they kill off victims before they can infect others. That latency between exposure and onset of symptoms (leading to death) is important, since viruses that are too lethal (i.e. too fast-acting) end up wiping themselves out of existence by killing their hosts before they can pass on their viruses to other hosts. So in fact, there IS a limiting factor to virulence, namely, the need for a living host.
IluvTTATT asked- Also, are there different rates of evolution? Is there something that can accelerate it?
Sure: exposure to ionizing radiation, for one. There are also chemicals which are known as 'mutagens' which also chemically accelerate the rate of mutations by interfering with the replication process of cells (and many of these chemicals are also considered 'carcinogens', since as I said earlier, there's a connection between rates of mutations and rates of various types of cancer; asbestos is a carcinogen that causes lung cancers).
Even flying in the passanger compartment of a jet aircraft at altitude exposes individuals to higher levels of cancer-causing radiation, which likely accelerates mutations of the genes that matter for evolution (not the genes found in the cells of the body, as much as alterations in the genes of the gametes, the sperm-producing and egg-producing cells).