The plans Lotus had prior to the Emira launch were based around the EU7 emissions regulations coming into effect in 2025/6, which is now under review and likely to change.
In theory Lotus could continue selling the V6 after EU7, in markets where it still meets regulations and isn't heavily taxed. But the V6 is already eye-wateringly expensive to tax in places like France, hence the push for the i4.
Lotus knew the V6 would become non-compliant under EU7, as Toyota weren't going to re-engineer it. The i4 will also be non-compliant but AMG have confirmed to Lotus they will update it to comply.
As part of the wider Lotus strategy, their EV sportscar (Type 135) was due to launch in 2025/6. That would have started phasing in at the same time as the V6 phased out. The intention is to build both Emira and Type 135 at Hethel, so the assumption was to build V6 and i4 until 2026, then drop V6 and continue i4 alongside Type 135, then eventually drop i4 and build only Type 135 once ICE sales stop. All this already depended on sales volumes and development timeframes, which are now also being revised alongside the change to EU7 timing.