Yes, media consolidation limits the number of expressed opinions because any viewpoints that are not supported or at least tolerated by the management of media companies will not be promoted by them. Opinions which are not in the interest of media companies will not be heard by any audience that isn't actively seeking them out. This severely limits the number of expressed opinions available to most people.
I think the more media outlets there are the more different viewpoints and takes you get on a piece of news, when you start to merge them together you get a generic right and a generic left take on a piece of news instead of a more in depth analysis.
Yes, the consolidation of media limits the number of opinions that are expressed. As fewer media places exist in order to express opinion, it is only logical that this also causes fewer opinions to be expressed. Newer media sources arise and do offer new places to express opinion, but so many times, these new media are absorbed by established firms.
Yes, consolidating various media outlets would surely reduce or limit the number and types of opinions that are being expressed. With a large variety of media outlets, many individuals can express their many viewpoints, but as media outlets consolidate, that will lessen. Typically a singular media outlet is at least semi-cohesive with their overall opinion or spin.
Media consolidation does not limit the number of opinions that are expressed as there are so many forms of expression. In the light of the Internet, people will likely start creating their own news sources based on events that are taking place in their local communities. The number of so-called professional journalists may decline, but that will spark in incline in local journalism.