The 19-year-old Brazilian joined Lyon from Madrid on loan in January after falling out of favour under then-head coach Xabi Alonso. He ends his spell in Ligue 1 with eight goals and seven assists in 20 appearances, having been central to Lyon's push for a Champions League qualifying place.
Fonseca spoke ahead of Sunday's final league fixture against Lens, which Lyon need to win to secure fourth place and retain their route into next season's Champions League.
"For Endrick it will be difficult to stay here. Real Madrid will certainly want him back. That's normal. After what he has shown here, he has proved he has the quality to be a Real Madrid player."
Real Madrid have already communicated to Endrick's camp that there will be no further loan. According to AS, the club intend to integrate him fully into next season's squad, with a role envisaged both as cover for Kylian MbappĂ© in the centre-forward position and as an option on the right wing alongside MbappĂ© and VinĂcius JĂșnior. Rodrygo Goes is expected to return from injury, adding to the competition for places.
Endrick is among Brazil's pre-selected players for the World Cup, where he is expected to feature. The tournament gives him a further window to demonstrate his development before reporting back to Madrid.
Fonseca indicated the summer transfer activity at Lyon will be significant and that Endrick's departure is one of several he expects to confirm.
"Maybe for some players this will be their last game."
Madrid paid Palmeiras a fee of up to 60 million euros for Endrick, with the transfer completing in July 2024. The club regard him as a long-term asset and are not open to a sale.