>>7
Yes, it is true that R7RS-large is within the ratification process. This means that there is the potential within the process for -large to change its details such that the definition of -small does not become a proper subset of -large. My crystal ball prophesy of the final R7RS-large standard is that the small standard is going to be a proper standard of the large standard.
The reasoning for this is based on the context of why there are large and small standards for the same language: it will be a practical language for the largest amount of software developers. There are real world applications in which only a "basic" amount of programming logic needed to fulfill the job; the small standard is good for these kinds of software applications. In real world practice, it has been shown that the different Scheme implementations re-implement functionality between the implementations that are not currently part of the standard. This is the motivation of why there are Scheme Requests for Implementation (SFRIs). The large standard is good for the wider world of applications that's practically used in the wide world: the functionality in the large standard is because we know for a fact that the specific function pieces are widely used.
So it the case that the large standard is an extension (a superset) of the small standard; I couldn't fathom a practical reason to justify designing the large standard so that isn't the case. Despite knowing nobody within the Scheme committee, I'm very confident that the ratified R7RS-large standard will be a proper superset of the R7RS-small standard; thus all conforming -small implementations will be compatible to all conforming -large implementations.