If the universe is infinite now it has always been infinite. This is the opinion of many astronomers today as can be concluded from the following series of interviews, but the opinions differ much more than I had expected. Many astronomers do not have a clear opinion on this matter. Others have a clear opinion, but very different from the majority. Detailed arguments by two experts on general relativity are also included. Observations show that the universe is flat, i.e. the curvature is zero within the small uncertainty of measurements. This implies an infinite universe, though most probably we will never know that for certain. For comparison with the recent interviews, opinions during the past 2300 years since Aristotle about the universe being finite or infinite have been collected from literature, and it appears that the scientists often had quite definite opinions.English is probably not his native language, so I shouldn't blame him for the misspelling in the title.
I am not sure the question is meaningful. Some think that the universe is spatially infinite, but that matter only occupies a bounded portion of it. Should such people say that the universe is finite or infinite?
I say finite. We can only observe a finite portion of the universe, and our physical theories relate to finite quantities. I am not sure it makes any scientific sense to speak of an infinite universe.
The whole concept of actual infinity is dubious:
The legendary Carl Friedrich Gauss denied that anything infinite really existed, saying "Infinity is merely a way of speaking" and "I protest against the use of infinite magnitude as something completed, which is never permissible in mathematics."