You do mean that princess Estelle is the namesake of the countess, don't you? (I doubt Estelle Manville was named after a princess born 112 years later.)
That is not the true Estelle cake, it's an ordinary Princess cake with a pink covering made to the christening of Estelle.
Estelle got her own cake in her duchy, there was a competition and Lanemo konditori (bakery) in Linköping won:
Östgötska hertiginnan prinsessan Estelles egen bakelse - Sett och hört - www.ostgotamat.se
There were also an Estelle cake made in Ockelbo:
Ockelbos lilla sessa får en egen bakelse
The same bakers who made the Estelle cake in Ockelbo made a cake to Leonore:
Tårtan smakar kungligt, Leonore! | Nyheter | Expressen
I haven't seen any kind of cake made for Nicolas, but there is a Finnish Nikolai cake, but I wouldn't recommend it for the little prince until after his 18th birthday as there are beer in the cake:
Nikolai-kakku – Olut ja suklaa –reseptikilpailu - House of Beer
As for the cake for prince Oscar, it seems to be an ordinary Princess cake, but with blueberries and a white covering. It would have been more interesting if they had taken the Oscar II cake and made something new of that:
Oscar II:s tårta | Recept från Köket.se as it's a gluten-free cake.
Even Sofia have got her own cake in Älvdalen:
https://www.youtube.com/watch?v=fi_ppPAOHGUhttp://www.theroyalforums.com//www.pinterest.com/pin/create/extension/