The phrase "so soon" can be replaced by a variety of synonyms, depending on the context and tone of the sentence. Some examples include "prematurely," "unexpectedly," "abruptly," "hastily," and "immediately." Using different synonyms can add variety and nuance to your writing, providing a more detailed and descriptive account of events. For instance, if you want to convey a sense of urgency or impatience, you might use words like "urgently," "eagerly," or "impatiently" instead of "so soon." Alternatively, if you're trying to express a sense of disappointment or regret, you might opt for words like "regrettably," "unfortunately," or "alas," in place of "so soon".