God is not at war with time, He is at war with sin. That is what won't exist in eternity but time definitely will.
You can't have sequence without time, sequence implies time, as in it will be possible to measure one set of activities in relation to another set of activities, which is how we measure time.
If everything happens at once then its not a sequence, that's stuff happening simultaneously, (another time related term btw). You can't have A cause B but have A & B happen at the same time.
Just for clarity, while God may be outside our timeline, and maybe even above heavens timeline, heaven, angels etc all have a timeline, possibly even God himself, but that does not mean He changes (unless He wants to)
There was a time before God created anything and a time after
There was a time before angels and a time after
There was a time before Satan and a time after
there was a time before Satan rebelled and a time after
there was a time before a third of angels sinned and a time after
There was a time before a war in heaven and a time after
there was a time before the Word created the world (universe) and a time after
There was a time before the angels rejoiced at God's creation of the world and a time after
There was a time before the creation of man and a time after
there was a time before Jesus was born as a human and a time after
there was a time before Jesus crucifixion & resurrection and a time after
There was a time before Jesus's ascension to heaven and a time after
There was a time before Jesus went to prepare the 'mansions' for us and a time after
There is a time before Jesus leaves heaven to return to earth and a time after
Most of the things in that list have a heavenly component or occur in heaven. There was a time before them & a time after them so time does exist in heaven.
In heaven, as now, if you have so much as a thought, there will be a time before that thought & a time after that thought.
In eternity, we won't age or decay (not that time causes that, it doesn't) but there will still be time, an endless amount of it
.
Lastly, don't overlook Revelation 22:2, in the chapter describing the new eternal state. What word do we find there, in the very verses on eternity: the word
month - a very much TIME based term.