The phrase "that is to be" can be replaced with several synonyms, each conveying a slightly different meaning. "Forthcoming" suggests something anticipated and expected, while "impending" is more urgent and suggests something about to happen imminently. "Future" implies a time that is ahead, while "prospective" suggests something that is likely to happen but not yet guaranteed. "Planned" and "scheduled" are both useful synonyms for something that has been arranged in advance, while "anticipated" suggests something that is expected to happen but not yet certain. Ultimately, the specific synonym used depends on the context and intended meaning of the phrase.