The 21-year-old, who suffered a slight hamstring injury, was named in the side's 32-man squad, but Declan Kidney gave out mixed signals about who will fill the number 10 jersey at the Aviva.
Jackson was on the bench for Tuesday's training, and with Jonathan Sexton ruled out by the medical team, the position seems to be wide open to the Ulster star and Ian Madigan.
The Belfast man is expected to be back on Thursday, but if he fails to recover then Madigan will start and Ronan O'Gara could make a comeback.
O'Gara, who is Ireland's most capped player ever, was left out of the side following poor performances against England and Scotland in previous Six Nation matches.
Kidney told press Jackson would start, before saying he would not reveal his decision between Jackson and Madigan until Tuesday evening.
But a few minutes later, he said the call had been put back to Thursday and although he knew the identity of his fly-half, he would be keeping it to himself until he had spoken to the two players.
Kidney said he would "not mind" asking O'Gara to come back to the international side.
"There was no fun whatsoever in leaving him out. I'd only be too delighted. It wouldn't be an awkward conversation from my side, absolutely not.
"I'm sure he'd love to play for Ireland, he's always loved playing for Ireland and he'd continue to do that.
"Ronan will have been disappointed. You don't give the type of service that Ronan has given and not be disappointed," he added.
Kidney said it was his role to make the all and played down the decision not to name O'Gara in this weekend's line-up.
"Everybody is centrally contracted, so everyone is available to play for Ireland at any stage," he added.
Elsewhere Leinster's Fergus Madden will step in for Craig Gilroy after medics said the Ulster player had not recovered from his groin strain.
Cian Healy is back at loosehead prop following his ban for stamping an England player last month.
That means Tom Court is back on the bench, along with Donncha O'Callaghan.
He was standing in for lock Mike McCarthy, who has now recovered from knee ligament damage, while a replacement for injured substitute prop Declan Fitzpatrick has yet to be announced.
Ireland team in full:
R Kearney (Leinster); F McFadden (Leinster), B O'Driscoll (Leinster), L Marshall (Ulster), K Earls (Munster); AN Other, C Murray (Munster); C Healy (Leinster), R Best (Ulster), M Ross (Leinster), M McCarthy (Connacht), D Ryan (Munster), P O'Mahony (Munster), S O'Brien (Leinster), J Heaslip (Leinster, capt).
Replacements: S Cronin (Leinster), D Kilcoyne (Munster), AN Other, D O'Callaghan (Munster), I Henderson (Ulster), E Reddan (Leinster), AN Other, L Fitzgerald (Leinster).