I know that it sucks for you guys that Neymar is staying, because it will mean that the clubs who were chasing him will look after Kun now. But you shouldn't be that worried.
I don't think Real will sign Aguero, they'll just wait for Neymar to make his move next season, maybe even in January.
And City don't need Aguero, they have Tevez, Dzeko and Balotelli and they are looking after Nasri, so no place for Aguero.
Chelsea is the club to be worried about, Villas-Boas likes his 4-3-3 and Aguero would fit in his plans, but I doubt they sign Modric/Moutinho, Falcao and Aguero in one summer.
Inter would be ones to be worried about if they sell Eto'o.