AGAINST a Sri Lanka NEL:
The Road Block limit. Since they're limited to six each, that means there are twelve Road Blocks in total, and only two left -- with both the sewing in Sri Lanka and the tightrope in Singapore confirmed as Road Blocks. This leaves no Road Block in Perth.
On the two previous occasions an ActiveTV race has had back-to-back NELs, the first one has involved money-stripping rather than an MFE penalty. If Sri Lanka was a NEL, then in theory Sam/Renae would have been mugged.
FOR a Sri Lanka NEL:
News report that mentions Renae doing a tightrope task in Singapore says that IF she makes it through, they'll be racing in their hometown -- there's no IF about it if there's no elimination in Singapore.
Presskit mentions three non-eliminations, "each" with the MFE penalty -- Kutna Hora had no penalty, therefore is probably not one of the three NELs.
Seven's love of two-hour finales -- while the US didn't have one from TAR9 to TAR18, Australian viewers have had two hour finales in every season since TAR12 (although most seasons in that range had episodes burnt off in chunks of double episodes).
It's been tradition in final legs since TAR10 to either have no Detour or no Road Block, with only TAR12 deviating, which would mean the lack of one in Perth is irrelevant. (They could also be reinventing the two-RoadBlocks-in-one-leg twist from TAR16 by having two Detours in the same leg?
The presskit mentions a Yield appearing at some point in the race. It cannot be in the final leg, and I'm almost certain not even ActiveTV would put one in the F4 elimination.