The key to your question would be where was A2M ranked not this...

The key to your question would be where was A2M ranked not this quarter but the last two quarters. Companies can drop off for 2 quarters before they get deleted in an index.

If just looking at the current Q A2M will be survive..... Basing that it would have been in in 60th to 80th position last rebalance.

But in the next rebalance, if A2M is not in 98th or higher.....
If just one ASX 200 index company in position 101th to 106th qualify to join ASX100, it might survive.
If more than 2 qualify it would be 50/50.
If more than 3 qualify it would be curtains.

Note: ASX 100 and 200 index is not the largest 100 or 200 companies by market cap. Index do not include most broad index tracking ETF for example STW.

Also has daily, monthly share turnover and few other metrics come into play for stability.

A2M position in relative indexes
ASX 100 = 100th
ASX 200 = 107th

Contenders 101 to 106 in ASX

	101	NXT	NEXTDC Ltd
1	102	AWC	Alumina Ltd
2	103	LYC	Lynas Rare EARTHS Ltd
3	104	IPL	Incitec Pivot Ltd
4	105	PMV	Premier Investments Ltd
5	106	RWC	Reliance Worldwide Corporation Ltd
6	107	A2M	The a2 Milk Company Ltd