I do not believe that purchasing a starter pack will prevent any more from being offered; in the years that I have been active in the forum, I've seen no evidence of this - neither personally nor from the community. The most likely scenario is that the account that was receiving the offers simply leveled up to a point that it is no longer eligible for the starter offers.
Bottom line: If a player is interested in the VP offer and is comfortable spending their money on the game, they should feel free do so without worry. In-game purchases have zero impact on the rest of the gaming experience other than providing the purchased items. Purchases will not increase or decrease a player's odds at any promotional opportunities or sales that may or may not show up in the future.