1.2 Normative References, Unicode version 6.3.0 - or later?

The citation of a specific version of Unicode, without more, does not allow for applications that conform to a later version of Unicode to conform to your specification.

For example, under 1.4.1.2 UTF-8 encoded strings, you say in part:

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The encoded data MUST be well-formed UTF-8 as defined by the Unicode spec [Unicode63] and restated in RFC 3629 [RFC 3629].
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I take that to be a normative statement that requires conformance to UTF-8 as defined by Unicode version 6.3.0. Do you agree?

That would mean an application that conforms to Unicode version 7.0, would not conform to your specification, even if it meets all other requirements.

I don't think that was your intent.

There is a phrase used in ISO work that might be adaptable to your situation:

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The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
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I would have 1.2 Normative References as your title and then use the last two sentences, thus:

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For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
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That gives you the flexibility to decide if you want to define conformance against a particular version of a normative reference or if you want to allow later versions of the same reference to be used for conformance purposes.