The players’ unions are now satisfied that last week’s reported threat from an al-Qaeda cell was “not credible”.
But they are yet to receive confirmation that regional police will implement the IPL’s security plan.
May told BBC Sport: “If the security situation does not improve, there could be mass withdrawals.”
The third season of the IPL begins in Mumbai on 12 March and several overseas players are due to fly out this weekend to join their franchises.
Essex all-rounder Graham Napier told BBC Sport he was still planning to fly today to join up with the Mumbai Indians, unless he received guidance not to.
Middlesex batsman Owais Shah said he would wait for advice from the Professional Cricketers’ Association before travelling to join the Kolkata Knight Riders.
And Hampshire all-rounder Dimitri Mascarenhas told The Times newspaper his “gut feeling” was that he would be joining the Rajasthan Royals on Thursday.
May, the chief executive of the Federation of International Cricketers (Fica), said it was regrettable that players were still unclear about security arrangements for the tournament.
“There are just 13 days before the start of the tournament and security arrangements have still not been agreed,” he said.
“We would love to tell the players it is okay for them to go – after all, we are the only party involved that isn’t conflicted here and doesn’t stand to profit from the IPL.
“But we can’t give that assurance at the moment, because no-one will say definitively that the security plan will be implemeted at each of the venues.”
IPL commissioner Lalit Modi has always insisted that security plans were in place and that the tournament would go ahead as scheduled.
Speaking on his Twitter feed on Friday, Modi said: “Spent whole day on security briefings venue by venue. Team done a great job in putting the plan together and have started the implementation.”
Matters are hardly helped by the fact that Modi refuses to talk directly to FICA or the national players’ associations.
However, some progress has been made, with national governments and independent adviser Reg Dickason, who has been contracted by the associations to look into security at the IPL, satisfied that last week’s threat from an al-Qaeda cell was not credible.
Asia Times online had published a message reported to be from the 313 Brigade, an operational arm of Al-Qaeda, that threatened the IPL, Commonwealth Games and Hockey World Cup, all of which are being held in India.
Yet the British, American, South African governments have all agreed the threat was not credible, as has Dickason.
Eight English players are due to take part in this season’s IPL – Kevin Pietersen, Paul Collingwood and Eoin Morgan, who will miss the first three weeks because they are on England’s tour of Bangladesh, and Napier, Mascarenhas, Shah, Michael Lumb and Ravi Bopara, who will be there for the duration.
The tournament was moved to South Africa last year because of concerns that security might be stretched in India because of the national elections.
