The phrase "which is to come" from verse 8 is connected to the rest of the verse having to with being "Alpha and Omega". The Most High is that which is, was, and will be (which is to come). It has nothing to do with Jesus coming on the clouds in verse 7. Again that is not Jesus speaking in revelation 8:
Revelation 1:7-8
7 Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen.
8 I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty.
So now with everything in context, we can look at the two controversial verses. It is clear that verse seven is speaking about The Messiah... not only because of him being pierced, but also because verse 1 says this is a revelation of him. However, we learned in verse one that it was The Father through His angel that was giving the Revelation... not The Messiah. This is why verse 7 is not in first person when speaking about Jesus... where as verse 8 is in first person. We also see the phrase "which is, and which was, and which is to come", which belong to a separate being from Jesus as we saw in verses 4-5. Lastly, we have the title "The Almighty" which refers To The Most High many places in scripture, but nowhere is it used to refer to Jesus.