Although Sri Lanka needs a near-miracle for that to happen, theoretically this how the remaining matches of Group 1 should end up, including Net run rate, for Sri Lanka to go through.
Sri Lanka also need to win big against the West Indies and also hope all other matches, except the England vs South Africa game will be close games. In this match, Sri Lanka would want South Africa to lose badly against England.
Group 1 remaining games :
* S Africa Vs Bangladesh : Bangladesh should win
* Aus Vs Bangladesh : Bangladesh should win
*West Indies Vs SL : Sri Lanka should win
*Australia Vs West Indies : West Indies should win
*England Vs S Africa : England should win
In this scenario, England will top the group with 10 points with 5 wins while all the other teams will end up with 4 points each with 2 wins
If Sri Lanka can get their NRR above all other four teams, they can get to Semi finals as the 2nd team. (CricWire)
Although practically it’s near-impossible, it’s still therotically possible with a miracle.