When we sailed Oosterdam this past December in an SC Deluxe Veranda, we were definitely able to go to the Pinnacle for breakfast. This was a perk listed on the HAL website and brochure for deluxe suite passengers. Check the website and with your TA. I haven't heard of this perk being taken away.
Would appreciate hearing back from you as to the outcome. The Pinnacle was MUCH better than alternate breakfast choices.