It could not have lasted. Not as a bunch of warring states as written.Just looking purely at the Rebellion (so forget about Virus), could it have gone on indefinitely? By that I mean the Imperium fracturing into a bunch of smaller sized states, and these states enduring generations into the future as separate entities, maybe some still nominally claiming the now meaningless title of Emperor and sometimes sparring. It could be a bit like post-Roman Europe or China's Warring States, or like Battletech's Succession Wars.
When first presented in the Imperial Encyclopedia, it was written as sufficiently vague that you could think each of the "factions" was out to capture Lucan's Imperium or Lucan get someone else's and thus get the Imperium back together thru eventual conquest.
Then Rebellion Sourcebook came out. There you find out the implied goals of each faction. At the time it was written (IY 1120), only Deneb, Lucan, Margaret and Strephon are making claims that an Imperium is still possible, even if it is lip service. Dulinor has already renamed his realm the Federation of Ilelish (1119). Strephon gets written out soon after with the IRIS thing (1121).
I see one thing that would have happened if things had gone on as written minus Virus stomping in 1130.
Astrogators' Guide to Diaspora shows they Solomani had a large number of systems that far coreward with Vegan refugees going to Daibei. My speculation is they would had their way with the Vegans. Genocide or whatever horrible fate you envision.
This does not take into account events occurring in 1128, 1129, and 1130 as written in the 1248 books like
- Solomani Confederation signs a formal cessation of hostilities with Margaret's Domain in 1129.